To compare the measurement of blood pressure on the upper arm and ankle during lower segment caesarean section under spinal anaesthesia

Abstract

Introduction: We have previously reported that there is failure of non-invasive blood pressure measurement (NIBPM) during caesarean section under spinal anaesthesia in over 50% of cases.a We felt that errors would be less likely if NIBPM could be taken at the ankle as it is immobile during caesarean section. The purpose of our study was to determine whether NIBPM on the ankle was equivalent to the arm. Methods: Following ethics approval, informed consent was obtained from thirty women scheduled for elective caesarean section. Two non-invasive blood pressure cuffs, one on the upper arm and one on the ankle, were used to measure blood pressures at three timed intervals - before spinal insertion, immediately after spinal insertion and after delivery of the neonate. Results: When readings were averaged, we found them to be virtually identical. However, using the method of Bland and Altman 2 we found that individual readings varied widely and that the 95% confidence intervals lay well outside our limits of agreement of 10 mmHg. In the case of mean blood pressure the average difference was 3.2 mmHg with 95% confidence intervals of 4-24.5 mmHg. Bland and Altman plot of arm vs ankle mean blood pressures. 40